Many people, especially diabetics, who suffers from long term complications such as ischeamia and neuropathy or patients confined to their bed are known to develop ulcers on foot, hip or sacrum. Foot ulcers are usually located on the planter or on the side or dorsum of the foot. Foot ulcers are induced by changes in bone structure, which can lead to protruding prominences and reduced thickness of the subcutaneous layer that ensures distribution and relief of the pressure applied to the foot.
The development of foot ulcers are i.e. dependent on a combination of etiology and the induction of pressure. There are essentially two mechanical inducers for pressure sore development, the stress of permanent (static) pressure and the stress of short term (dynamic) pressure.
The permanent or static pressure is when exertion of pressure over a long period (hours typically) is leading to the risk of collapse of veins and arteries. The collapse of these blood vessels may lead to ischemia e.g. lack of oxygen and nutrition and a build up of waste materials. These events may eventually lead to development of ulcers. The tendency is the longer period of pressure induction, the lower pressure is critical and may cause damage.
Short term or dynamic pressure impact is in the form of repetitive mechanical stress. This occurs e.g. when walking, where a typical pre-stage to ulceration is callus build-up. This type of ulceration may be compared to benign sanguinous blister formation. Critical pressure level of this type of pressure impact is much higher than in the case of a long time pressure load.
Dressings designed to manage wound healing and exudate are well known in the art. However, they do not take into account the effects of the pressure stress.
From International Patent application No. WO 91/01706 A1 (Smith & Nephew) is known a polymeric foam absorbent dressing for exudate handling in wound healing. No pressure relief/distribution properties are mentioned. This dressing comprises a foam material all over the surface. Since this open cell foam is designed to allow transportation of exudate, it has inadequate strength towards pressure, and will be compressed or collapse when worn on a foot.
WO 99/01166 A1 (Coloplast A/S) discloses a non-fibrous polysaccharide wound dressing capable of handling wound exudate by gelling properties. This material is very soft and gentle towards the ulcer. However, it has inadequate strength towards mechanical pressure and will collapse if pressure is applied.
Examples of pressure reducing/distributing/shock-lowering orthopaedic materials and products are also known:
In international Patent application No. WO 90/09746 A1 (Bernard, M.) is disclosed a composite inner sole for sports shoes, comprising a shock absorbing layer. No wound healing or exudate absorbing properties are mentioned.
U.S. Pat. No. 5,488,786 (Ratay, E. J.) discloses a highly resilient insole, designed to cover the hole sole of the shoe i.e. the whole plantar surface of the foot. No wound healing or exudate absorbing properties are mentioned.
Only few examples of a combining the two said properties are known:
From DE patent application No. 35 39 533 (Liedtke) is known a foam dressing. The dressing comprises a foam body, the non-skin-contacting surface optionally being covered with a film and the outer periphery of the skin-contacting edge covered with an adhesive. The foam serves both as a pressure reducing and distributing element and as an absorbent element. Between the adhesive-covered edge and the non-adhesive central part is a groove in the foam, as well as more grooves or indentations may appear in the central part. These grooves are made to enhance the flexibility of the dressing. The dressing is made of a single piece of foam, and the only barriers to control the wound exudate is the top film and the adhesive, leaving a severe risk of maceration when used on exuding wounds. In one embodiment of the invention, the dressing comprises a slit in the foam defining a lid to be opened and an absorbing pad may be inserted over the wound. However, this construction with a slit may give rise to problems with leakage.
GB patent No. 842 847 (Scholl) discloses a corn dressing, comprising a foam ring, serving as a pressure distributing part and a thinner central part with a napped inner side having a shock absorbing/cushioning effect. In the cavity between the central part and the skin/treated area a pad with medication may be placed. The reference is silent with respect to wound treatment as well as use of absorber, on the contrary, the device is donating medication to the treated site.
International Patent application No. WO 93/01777 A1 (Malloul, L.) discloses a dressing for sutured wounds. Said dressing has a foamed shock-absorbing element or cushion layer on both sides of the wound, protecting the wound from impact or pressure, and an area spaced apart from the wound with a pad right over the wound. The dressing only copes with dynamic pressure in the form of sudden impacts, and is silent with respect to static pressure.
European Patent No. EP 0 164 319 (Coloplast A/S) discloses a wound dressing of the hydrocolloid type with a pressure relief system of foam. The pressure is distributed through the foam in order to relieve the pressure on the ulcer. The dressing offers a possibility to adapt a specific relief area corresponding to the size of the ulcer, rendering it possible to transfer the pressure from the wound site to the surrounding healthy tissue. The pressure relief is described as having static pressure relieving properties, not dynamic pressure/shock relieving properties.
Diabetic patients are often suffering from neuropathy, rendering their sensibility skills to be greatly diminished or they may even suffer from a complete loss of feelings in the lower extremities, and especially in the feet. The patient will often fail to notice or be aware when individual points of a foot are subjected to severe constant pressure or repetitive stress, for example during long periods of standing or by use of badly fitting shoes, inducing the development of an pressure sore. Since metabolism is disturbed and blood circulation already can be reduced in diabetes patients, healing of such sores is most difficult.
Attempts have been made to prevent the development of pressure sores and ulcers in a patient who might not be able to recognise presence of severe sore inducing condition.
Dressings with different kinds of indicators are known, e.g. from European Patent application No. 430 608 (E. R. Squibb & Sons, Inc.), which discloses a wound dressing comprising a temperature sensing liquid crystal tape, affixed to the backing layer. A temperature change may indicate a change in wound condition. In the reference is also mentioned the possibility of a pressure indicator in the form of a piezoelectric element.
U.S. Pat. No. 5,642,096 (Paromed Medizintechnik GmbH) discloses a device for prevention of ulcers on the feet of diabetic patients. The device includes a pressure and temperature sensor in the form of a piezoelectric element carried in the innersole of the shoe. The patient is warned by a signal, e.g. a buzz if the pressure reaches a critical level. The device is constricted to the innersole of the shoe, and does not cope with detecting impacts to other body parts e.g. the side of the foot or on hips or sacrum, and it is also technically complicated and expensive.
Until now a dressing being capable of both handling wound exudate and at the same time relieving both static and dynamic pressure has not been disclosed.
It has now surprisingly been found that the above mentioned problem can be overcome by combining a shock-absorbing material with a moisture-absorbing material rendering it possible to obtain an effective and durable dressing suitable for both wound healing and prophylaxis of pressure ulcers as well as for protection of fragile skin.